The present invention relates to festoon assemblies of the type used with web processing equipment, and more particularly, to inertia compensated festoon assemblies usable to control precisely the tension in a web that is subject to tension changes and that is moving at a relatively high speed to and through web processing equipment.
Inertia compensated festoons are known and recognized in the art as excellent means for preventing fluctuations in tension in one region of a moving web from causing tension changes in another, downstream region of the web. As explained in U.S. Pat. No. 3,659,767 issued to John R. Martin, one of the inventors of the present invention, such inertia compensated festoons include a single inertia compensated "floating", "dancer" roller or multiple inertia compensated floating, dancer rollers. Following the teaching of U.S. Pat. No. 3,659,767, the assignee of the present application has for many years included either single or multiple floating dancer roller inertia compensated festoons as an integral part of its web butt splicers, and other similar high speed web handling equipment that are sold for use with web processing equipment. These festoons have admirably performed their intended function. More specifically, they have accurately controlled the tension in the moving web and have, for example, provided the web storage needed to permit a zero-speed butt splice to be made while the downstream portion of the web on the expiring roll continues to be fed, at normal speed, to the continuous web processing equipment, as for example, a printing press.
In certain applications that require webs to be run at relatively high web speeds and under relatively low tensions so as to avoid permanently deforming the webs during operation, it has been found that the heretofore available inertia compensated festoons are not completely suitable. For instance, recently it has been proposed to run the fragile, low modulus of elasticity webs used to make disposable diapers at the relatively much higher speeds of eight hundred to one thousand feet per minute (instead of around six hundred feet per minute). These operating speeds require that a multiple dancer roller festoon be utilized. Otherwise the assembly would not have sufficient web storage capacity so as to enable the web to continue running, at such relatively high speeds, to and through the disposable diaper making line during the frequent zero-speed splices. However, at these relatively high speeds and with these low modulus of elasticity webs, it has been found that the prior multiple dancer roller inertia compensated festoons do not always provide accurate enough tension control. The reason for this, it is believed, is that the web stretches in the web spans between the multiple rollers in the festoon. This stretch was not contemplated in the discussions in U.S. Pat. No. 3,659,767. As a result, not all of the tension variations or fluctuations in the web are removed.